This proposal describes research on inflectional and derivational morphology and their role in reading and related tasks. Morphology is the aspect of language concerning the forms of words. The issues to be addressed concern how this information is represented in lexical memory; how it relates to other types of information including orthography, phonology, and semantics; and how it is used in processing. The research utilizes both behavioral studies of skilled language users and computer simulation modeling. The issues are framed in terms of connectionist principles concerning knowledge representation, acquisition, and processing that were developed in previous research on reading simple, monomorphemic words. The proposed research attempts to extend this theoretical framework to the processing of more complex words. The main emphasis of the research is on the quasiregular character of inflectional and derivational morphology: the fact that both systems are productive and can be described as "rule-governed" but also admit many exceptions that deviate from what is predicted from the rules. These phenomena have standardly been treated within dual-route models of lexical access in which there are separate mechanisms for the rule-governed cases and exceptions. Connectionist models provide an alternative approach in which all forms are governed by a single network. The experiments focus on phenomena that differentiate the dual- and single mechanism approaches in both inflectional and derivational domains. The theoretical account is also tested by implementing computational models with the goal of simulating behavioral data in close detail.